Registered Partition Deed.

Hi, my grandfather has 6 sons say A to F and my father say B is the second son. we all have done partition of all the grandfather's property in 2002 under registered partition deed. A, has two sons, they were major then B, has three sons, two major and one minor then, C, has four daughter all minors then, D, has two daughters and one son all minors then, E, has two sons, both minors then and F, has two sons and one daughter all minors then. all have signed the documents and for minors their dads have signed the documents as legal guardians. Now A to F have challenged the registered partition deed in the civil court saying my father B has bossed over others and got the major share in the property. we have got four properties out of five of my grandfathers properties, other have got Rs.10000.00 as share. A, C, D, E and F have got properties where my grandfather has given them the money to purchase but now due to the ulterior motives they have challenged the registered partition deed in the court. Please advice me whether they can challenge the registered partition deed. how can we defend. The case has been put by daughters & sons and wives of D, E and F they being plaintiffs and A to F as Defendants. They say, we were minors when the partition happened and the share is not equal. Thanks